The present invention contemplates a system and method for altering the way a patient image, such as by X-ray, is viewed and obtained. More particularly, the inventive system and method provides means for decreasing the overall radiation to which a patient is exposed during a surgical procedure but without significantly sacrificing the quality or resolution of the image obtained.
Many surgical procedures require obtaining an image of the patient's internal body structure, such as organs and bones. In some procedures, the surgery is accomplished with the assistance of periodic images of the surgical site. Surgery can broadly mean any invasive testing or intervention performed by medical personnel, such as surgeons, interventional radiologists, cardiologists, pain management physicians, and the like. In surgeries and interventions that are in effect guided by serial imaging, which we will refer to as image guided, frequent patient images are necessary for the physician's proper placement of surgical instruments, be they catheters, needles, instruments or implants, or performance of certain medical procedures. Fluoroscopy, or fluoro, is one form of intraoperative X-ray and is taken by a fluoro unit, also known as a C-arm. The C-arm sends X-ray beams through a patient and takes a picture of the anatomy in that area, such as skeletal and vascular structure. It is, like any picture, a two-dimensional (2D) image of a three-dimensional (3D) space. However, like any picture taken with a camera, key 3D info may be present in the 2D image based on what is in front of what and how big one thing is relative to another.
A DRR is a digital representation of an X-ray made by taking a CT scan of a patient and simulating taking X-rays from different angles and distances. The result is that any possible X-ray that can be taken for that patient can be simulated, which is unique and specific to how the patient's anatomical features look relative to one another. Because the “scene” is controlled, namely by controlling the virtual location of a C-Arm to the patient and the angle relative to one another, a picture can be generated that should look like any X-ray taken in the operating room (OR).
Many imaging approaches, such as taking fluoro images, involve exposing the patient to radiation, albeit in small doses. However, in these image guided procedures, the number of small doses adds up so that the total radiation exposure can be problematic not only to the patient but also to the surgeon or radiologist and others participating in the surgical procedure. There are various known ways to decrease the amount of radiation exposure for a patient/surgeon when an image is taken, but these approaches come at the cost of decreasing the resolution of the image being obtained. For example, certain approaches use pulsed imaging as opposed to standard imaging, while other approaches involve manually altering the exposure time or intensity. Narrowing the field of view can potentially also decrease the area of radiation exposure and its quantity (as well as alter the amount of radiation “scatter”) but again at the cost of lessening the information available to the surgeon when making a medical decision. Collimators are available that can specially reduce the area of exposure to a selectable region. For instance, a collimator, such as the Model Series CM-1000 of Heustis Medical, is placed in front of an x-ray source, such as the source 104 shown in FIG. 1. The collimator consists of a series of plates that absorb most incident X-rays, such as lead. The only x-rays that reach the patient are those that pass through apertures between the plates. The position of the plates can be controlled manually or automatically, and the plates may be configured to provide differently shaped fields, such a multi-sided field. Since the collimator specifically excludes certain areas of the patient from exposure to x-rays, no image is available in those areas. The medical personnel thus have an incomplete view of the patient, limited to the specifically selected area. Thus, while the use of a collimator reduces the radiation exposure to the patient, it comes at a cost of reducing the amount of information available to the medical personnel.
Further, often times images taken during a surgical intervention are blocked either by extraneous OR equipment or the actual instruments/implants used to perform the intervention. Limiting the blocking of the normal anatomy behind those objects would have tangible benefits to the medical community.
There is a need for a an imaging system, that can be used in connection with standard medical procedures, that reduces the radiation exposure to the patient and medical personnel, but without any sacrifice in accuracy and resolution of an X-ray image. There is also a need for an imaging system that accounts for instruments and hardware, such as implants, that might otherwise obscure a full view of the surgical site.